Chronic wounds are still an important clinical concern since up to 50% of all cases that have been present for more than a year remain resistant to treatment. Therefore, understanding how wounds heal will help in the development of new treatments. Among different approaches, stem cell based therapy has shown great potential from preliminary findings in both animal models and human studies. However, the underlying mechanisms through which stem cells contribute to cutaneous wound healing have not been clearly delineated. The major focus of our laboratory is to examine the expression and function of a nuclear protein, named Kruppel-like factor 4 (KLF4), in tissue stem cells. KLF4 is a transcription factor that is highly expressed in differentiated epithelial cells including those of the skin. Indeed, KLF4 is required to establish the barrier function of the skin. KLF4 also has important functions in stem-cell biology, including the self-renewal of embryonic stem cells, and induction of induced pluripotent stem cells from well-differentiated fibroblasts with three other proteins, Oct4, c-myc, and Sox2. This proposal focuses on testing the hypothesis that KLF4- expressing stem cells have a critical function in mouse cutaneous wound healing. In support of this hypothesis, we have found, using transgenic mouse models, that KLF4 is expressed in mouse epidermal stem cells. Our preliminary data also showed that KLF4-expressing pluripotent cells, probably hair follicle stem cells, migrate from its original position toward the wound during wound healing, indicating that these cells have an important function in cutaneous wound healing. In Aim 1, we will validate KLF4 gene expression in mouse epidermal stem cells. In Aim 2, we will study the function of KLF4-expressing epidermal stem cells in mouse skin wound healing. In Aim 3, we will study the function of bone marrow-derived KLF4-expressing stem cells in mouse skin wound healing. We will use a novel inducible KLF4 knockout mouse model. Taken together, the proposed studies will not only provide novel information about the mechanisms by which KLF4-expressing stem cells function in mouse cutaneous wound healing, but may contribute to the development of novel strategies that selectively modulate the function of KLF4-expressing stem cells to promote cutaneous wound healing.